Raw material charging apparatus in a shaft furnace



United States Patent Japan 42/ 57811 ABSTRACT: A raw material charging apparatus in a shaft furnace for effecting an ideal charging of raw material into the furnace characterized by comprising a fixed hopper having several branched discharging ports in the lower part thereof,

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[54] RAW MATERIAL CHARGING APPARATUS IN A SHAFT FURNACE each of the discharging ports being provided with a material cutoff valve, a bell hopper installed below said fixed hopper, said bell hopper being provided with gas cutoff valves of the same number as said discharging ports and a rotary chute installed in the upper part of said fixed hopper.

[51] Int. F27b 11/12 Patented Nov. 24, 1970 Sheet FIG.

PRIOR ART FIG.2

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Patented Nov. 24, 1970 Sheet & 012

FIG.5

8 a Rm w 0 Th m ame W K mum t. iv -Jwl BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a raw material chargingapparatus for a shaft furnace, more particularly to an apparatus for charging material into a blast furnace operating under severe conditions such as under high pressure within the furnace, while preventing gases from leaking out.

2. Description of the Prior Art For a charging apparatus on the top part of a blast furnace, there has been heretofore widely adopted a structure, wherein a small rotary bell hopper is provided above a large bell in the top part of a furnace andits rotating part is sealed with water or grease to prevent gases produced in the furnace from leaking out. However, there are disadvantages that not only is the structure complicated but also the leakage of gases becomes severe with the wear of the sealing part. Particularly, with an increasing tendency recently to operate furnaces .at higher pressures, the problem of gas leakage has become more serious.

As a measure to meet this situation, there is already known a system wherein a large bell hopper and a small bell hopper are fixed and a rotary chute and a gas cutoff valve are provided above them so that the leakage of gases may be prevented by adjusting the pressures in two pressure equalizing chambers.

However, this apparatus has also disadvantages that, because it has a rotary chute in the upper pressure equalizing chamber, the maintenance of the apparatus is difficult and during the operation of the apparatus there is a danger of breakdowns on account of heat and dust, and moreover, because the rotary chute is driven through rods suspending the chute from above, the construction is very complicated, because there are provided triple rods, including the rods for suspending the large and small bells, which makes the replacement of the bells very difficult.

Further, for hoisting up raw materials to the top part of. the blast furnace, there have been, in general, adopted two systems, that is, a skip charging system and a conveyor charging system. However, with the latter system the uniform distribution of the raw material in the peripheral direction within the furnace can be more easily attained, because in this system the raw material is continuously fed in a fixed amount to the top of the furnace.

In the case of the above-describedapparatus, during the feed of the raw material onto the small bell from the skip or conveyor the gas cutoff valve is left open. Particularly, when using the conveyor charging system, the time during which the cutoff valve remains open is long but the time, during which the space between the small bell and the gas cutoff valve, that is, the upper pressure equalizing chamber is kept under the same equal pressure as the furnace top pressure, is so short that the wear of the small bell seat surface and in its turn also the wear of the large bell seat surface are accelerated. Therefore, the advantage of the two-pressure equalizing chamber type charging apparatus in preventing the wear of a large bell seat surface, as already suggested, is thereby greatly reduced.

As a modification of the application of this apparatus, there is known a system wherein a raw material storing hopper having a raw material cutoff valve in its bottom part is provided above the gas-cutoff valve so that the raw material from the conveyor will first be received in this raw material storing hopper. When the raw material stored in this hopper reaches a fixed amount, it may then be dropped onto the small bell by simultaneously opening the raw material cutoff valve and the gas cutoff valve.

However, in this system, because a large amount of the raw material is passed at once through the rotary chute, there is little difference in the charging of raw material between the conveyor charging system and the skip charging system, and thus the superiority of the conveyor charging system to the other material will be lost.

SUMMARY OF THE INVENTION In order to obviate the above-mentioned disadvantages the present invention provides a raw material charging apparatus for a shaft furnace which comprises a fixed hopper having several branched discharging ports in the lower parts thereof, each of the discharging ports being provided with a material cutoff valve, a bellhopper installed below said fixed hopper in connection with the latter, said bell hopper being provided with a number of gas cutoff valves the same as the number of said discharging ports and a rotary chute installed in the upper part of said fixed hopper. Alternatively the apparatus comprises a fixed hopper installed above the bell hopper, said fixed hopper having several branched discharging ports in the lower part thereof, in each of the discharging ports or in the vicinity thereof there are provided a gas cutoff valve and a material cutoff valve or a gas cutoff valve only, and a rotary chute installed in the upper part of said fixed hopper. By means of this arrangement the raw material discharged from a conveyor or skip may be uniformly distributed to each of the discharging ports of the fixed hopper by means of the rotary chute rotating continuously or intermittently, and may then be dropped on the small bell by opening the gas cutoff valves and material cutoff valves.

According to the apparatus of the present invention, not only can anideal charging of raw material be carried out without sacrificing the superiority of the conveyor charging system in effecting the uniform distribution of the raw material, but also a controlled segregated charging in the peripheral direction, which was never possible with any conventional apparatus, becomes simultaneously feasible. That is, an amount of the raw material locally required can be optionally distributed in concert with an apparatus for measuring the raw material distribution within the furnace. By properly selecting the time of opening the gas cutoff va ve and raw material cutoff valve of each discharging port, any raw material distribution may be formed on the small bell, whereby any desired raw materialdistribution may be obtained within the furnace.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertically sectioned view of a known furnace top charging apparatus, FIG. 2 is a vertically sectioned view of a modification of the apparatus of FIG. 1, FIG. 3 is a vertically sectioned view of a raw material charging apparatus according to the present invention, FIG. 4 is a sectioned view on line IV-IV in FIG. 3, and FIG. 5 in a graph showing the results of raw material distribution tests with a model of the apparatus of the present invention as shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention will be explained in detail with reference to the above-mentioned drawings.

FIG. 1 is a vertically sectioned view of a known charging apparatus having a rotary chute provided in a pressure equalizing chamber and having a gas cutoff valve provided in the lower part of a fixed hopper above said chamber. A large bell 1, large bell hopper 2, small bell 3 and small bell hopper 4 do not rotate. The large and small bells 1 and 3 are vertically movably suspended respectively with a large bell rod 5 and small bell rod 6 from above. Above the small bell 3 and small bell hopper 4 there is set a rotary chute 8 suspended with a suspending rod 7 and rotated with a driving device provided in the upper part of a sealed vessel. A proper number of fixed hoppers 12 each having a gas cutoff valve 9 are further provided-above the rotary chute. There are formed two pressure equalizing chambers, a lower one 10 between the large hell I and small bell 3 and an upper one 11 between the small hell 3 and gas cutoff valve 9 in order to prevent thereby the wear of the large bell seat surface.

However, this system has the following disadvantages. Because of the rotary chute 8 being situated within the upper pressure equalizing chamber in which a high temperature and dust prevail and its suspending rod 7 is a triple rod mechanism including the large bell rod and small bell rod 6, the mechanism is so complicated and is so difficult to maintain that troubles are likely to occur.

Further, it is noted that, when using a conveyor charging system, the time required for discharging the raw material onto the small bell 3 is so long that the gas cutoff valve 9 has to be kept open for a long time, and thereafter the time during which the pressure in the upper pressure equalizing chamber is equalized is relatively short, so that a great pressure difference is produced for a long time across the small bell 3, whereby the small bell seat surface will be worn by high speed gas jets containing a large amount of dust, and as a result thereof, the pressure within the lower pressure equalizing chamber will be reduced, resulting in accelerating also the wear of the large bell seat surface.

Further, there is known a modification of the above-mentioned apparatus, as is shown in FIG. 2. This modified apparatus is provided with a plurality of raw material storing hoppers 14 each having a gas cutoff valve 22 and a raw material cutoff valve 13 in the bottom part thereof above a rotary chute 21 so that, after a unit amount of raw material from a conveyor 15 has been stored first in the storing hopper 14, it may be dropped onto the small bell 16, passing through the rotary chute 21 within a short time, while simultaneously the gas cutoff valve 22 and raw material cutoff valve 13 are opened. Thus, the time, during which the gas cutoff valve 22 is being kept open, is reduced, while the time during which the pressure in the upper pressure equalizing chamber 7 is equalized is relatively long, whereby the wear of the seat surfaces of the small hell 6 and large bells can effectively be prevented.

However, the above-mentioned system must be operated on the other hand, at a sacrifice of an advantage the conveyor charging system possesses of being capable of uniformly distributing the raw material in the peripheral direction.

In general, in the case of a skip charging system the rotary chute should continuously be rotated or stopped to vary the position of the port of the rotary chute with every unit amount so as to form distributing cycles in turn, in order to uniformly distribute the raw material in the peripheral direction, because in this system the raw material is discharged in a large amount at once from the skip. On the other hand, in the conveyor charging system, several layers of the raw material are formed in the peripheral direction by the continuous rotary chute, whereby a uniform distribution of the raw material can easily be obtained, because in this system the raw material is discharged in a small amount at a constant velocity. But, in the case of the system shown in FIG. 2, because the raw material is first stored on the raw material storing hopper 14 from the conveyor 15 and is then passed in a large amount through the rotary chute 21, the distribution of the raw material will be effected in the same manner as in the case of the skip charging system, and consequently excellent distribution of the raw material will not be achieved.

FIG. 3 is a vertically sectioned view of a raw material charging apparatus according to the present invention. It is the same as in a conventional furnace top charging apparatus having a large bell 1, large bell hopper 2, small bell 3 and small bell hopper 4 which do not rotate and the large and small bells l and 3 being vertically movably suspended respectively with a large bell rod 5 and a small bell rod 6.

The apparatus of the present invention is characterized by being provided with a fixed hopper 29 having several branched discharging ports in the lower part thereof, each of the discharging ports being provided with a material cutoff valve 28, a bell hopper 32 installed below said fixed hopper 9 and connected with the latter, said bell hopper being provided with a plurality of gas cutoff valves 28 the same in number as said discharging ports, and a rotary chute 30 installed in the upper part of said fixed hopper 29 and supported on supporting rollers 31. In addition the bell hopper 32 can, if desired, at each of said discharging ports or in the vicinity thereof have a gas cutoff valve 27 in addition to the material cutoff valve 28. The rotary chute 30 can have means (not shown) coupled thereto to rotate it continuously or intermittently, so that the raw material discharged from the skip or conveyor may uniformly be distributed on the fixed hopper 9.

By means of the construction as above-mentioned the disadvantages of the conventional charging apparatus can be obviated. That is, as the rotary chute 30 and its supporting rollers 31 are outside the hoppers in the atmosphere, their maintenance is easy and the frequency of breakdowns becomes very low. As the raw material can be uniformly distributed in the fixed hopper 29 by the rotary chute 30, irrespective of whether a skip charging system or a conveyor charging system is used, a uniform raw material distribution can be achieved within the furnace.

There are some cases where the sinking velocity IV-if the raw material charge in the blast furnace is not uniform in the peripheral direction depending on the situation of the furnace. Even in such a case, however, any desired raw material distribution can still easily be obtained on the small bell 3 and therefore any desired raw material distribution can be formed within the furnace by opening required ones among the plurality of the raw material cutoff valves 28 and gas cutoff valves 27 somewhat later than the others or in turn at fixed intervals, which has been confirmed by the results of experiments made with a one-fifth scale model of a blast furnace charging apparatus.

FIG. 4 is a sectional view on line lV-IV in FIG. 3 and shows an example in which there are provided four material cutoff valves 28 lying in the positions of circumferential angles 0, and 270 respectively. Of course, the number of the material cutoff valves or the branched discharging ports of the fixed hopper is not always limited to four, but it may properly be varied as required.

FIG. 5 shows the height of raw materials distributed in the fixed hopper, on the small bell in the bell hopper and on the large bell according to the experiments made with the experimental charging apparatus having four branched discharging ports as described above, curve a showing the distribution of raw material, correspondingly to each of various positions of circumferential angles in the fixed hopper 29 and showing a lower height in the position of 30 than at other positions, curve b showing the heights of raw materials distributed on the small bell 3 as a result of the material being discharged through the discharging ports of the fixed hopper 29 by opening four material cutoff valves as shown in FIG. 4 in such a manner that the opening of the material cutoff valve in the position of 0 is delayed by about 0.5 second with respect to that of the other valves in the position of 90, 180 and 270 so that the raw materials dropped through the opening of the material cutoff valves of 90 [80 and 270 would slide towards the position of 0, whereby the lower height of the material in the position corresponding to 30 may be compensated when the material cutoff valve at 0 is opened after 0.5 second, and curve 0 showing the distribution of the raw material on the large bell under the same conditions as abovementioned.

Thus, by opening several raw material cutoff valves respectively at any time, any desired raw material distribution can be obtained and, by using them in combination with an apparatus for detecting the raw material distribution within the furnace, there can be carried out an ideal blast furnace operation in response to the raw material sinking velocity within the furnace.

As the driving mechanism and supporting mechanism for the rotary chute are all outside the hopper in the atmosphere, the maintenance and inspection of the rotary chute may be carried out with case, which makes the apparatus of the present invention very useful in practice.

We claim:

I. A raw material charging apparatus for a shaft furnace, comprising a fixed hopper having a vertical axis and having a plurality of branched discharging ports greater than three in the lower portion thereof, said ports being equidistantly spaced around a circle concentric with the hopper axis, a material cutoff valve in valving association with each of said discharging ports and having a valve operating mechanism coupled thereto, a bell hopper below said fixed hopper into which said discharging ports open, a plurality of gas cutoff valves in said bell hopper, one being in valving association with each of said discharging ports, and a rotary chute in the upper part of said fixed hopper and having rotating means coupled thereto, whereby the distribution of the raw material in the peripheral direction of the hoppers can be equalized.

2. A raw material charging apparatus as claimed in claim 1 in which said rotary chute rotating means includes supporting means for the rotary chute is intermittent rotating means.

5. A raw material charging apparatus for a shaft furnace,

comprising a fixed hopper having a vertical axis and having a plurality of branched discharging ports greater than three in the lower portion thereof, said ports being equidistantly spaced around a circle concentric with the hopper axis, a material cutoff and gas cutoff valve in valving association with each of said discharging ports and having a valve operating mechanism coupled thereto, a bell hopper below said fixed hopper into which said discharging ports open, and a rotary chute in the upper part of said fixed hopper and having rotating means coupled thereto, whereby the distribution of the raw material in the peripheral direction of the hoppers can be equalized.

6. A raw material charging apparatus for a shaft furnace comprising a fixed hopper having a plurality of branched discharging ports in the lower part thereof, a material cutoff valve in each of said discharging ports which serves at the same time as a gas cutoff valve, a bell hopper below said fixed hopper and connected with the fixed hopper, and a rotary chute rotatably mounted in the upper part of said fixed hopper.

7. A raw material charging apparatus for a shaft furnace comprising a fixed hopper having a plurality of branched discharging ports in the lower part thereof, a material cutoff valve adjacent to and in valving relationship to each of said discharging ports and which serves at the sametime as a gas cutoff valve, a bell hopper below said fixed hopper and connected with the fixed hopper, and a rotary chute rotatably mounted in the upper part of said fixed hopper. 

